The mechanisms of intestinal water and electrolyte secretion, its neurohumoral control, and the role of cyclic nucleotides in his process will be investigated in normal intestine perturbed by various transport altering compounds. Transport will be measured with the in vitro Ussing chamber technique, with measurements of isotopic influx across the intestinal brush border, with in vivo perfusion studies, and with radioimmunoassay measurements of cyclic AMP and cyclic GMP. The autonomic control of intestinal electrolyte transport will be studied through the use of cholinergic and adrenergic agonists and their blocking agents utilizing the techniques noted above. The mechanisms whereby large organic anions such as acetylsalicylic acid and phenolphthalein stimulate either sodium and chloride absorption or sodium anion secretion will be explored in depth. These studies should increase our understanding of the transport mechanisms residing in the intestinal epithelial cell membranes, should increase our understanding of the neurohumoral control of these processes, and should give insights into the possible agents which could be used therapeutically, in diarrheal states, to alter intestinal electrolyte transport. BIBLIOGRAPHIC REFERENCES: Farris, RK, EJ Tapper, DW Powell, and SM Morris. Effect of aspirin on normal and cholera toxin-stimulated intestinal electrolyte transport. J CLIN INVEST 57:916-924, 1976. Desjeux, JF, Y-H Tai, DW Powell, and PF Curran. Effect of cholera toxin on cellular and paracellular sodium fluxes in rabbit ileum. BIOCHIM BIOPHYS ACTA 448:352-367, 1976.